In Ext.layout.container.Card, getPrev() says it returns Ext.Component. When there is no previous item, it returns a Boolean. I (as I assume most) would assume it returns undefined when there is no previous item. Instead, it returns false.

That's because we're now using JSDuck to generate the docs, which doesn't require having @class and @extends if these can be implied from source.

That is correct But it is inconsistent. If we are using @ tags to document the code-base then we should do it correctly for the sake of quality and minimize the risk of having to implement edge cases in JSDuck.